Michaela Whitbourn

Terence Martin kept meticulous records of his sexual exploits. The former Tasmanian MP and mayor had a spreadsheet and hundreds of photographs detailing his encounters with sex workers – 162 in all, over 506 different occasions.

Calombaris pleads guilty to assault

Can your brain make you commit a crime?

Neurolaw is the term given to the use of brain scans as evidence in court. But what does it mean for criminal law in Australia?

One was a child prostitute. The 54-year-old insisted he thought "Angela", offered for sex by her mother and her pimp via a newspaper advertisement describing her as 18 and "new in town", was over the age of consent. She was 12 years old.

This is not simply a grim story of child exploitation, although it is certainly that. Martin's hypersexual, compulsive behaviour was traced to the medication he was taking for Parkinson's disease.

'Brain fingerprinting' could be a useful tool in fighting terrorism. But it raises plenty of moral questions.

A Tasmanian Supreme Court jury found him guilty of unlawful sexual intercourse with a young person in 2011. But the court accepted the evidence of a neurologist and a forensic psychiatrist that he developed hypersexuality and an impulse control disorder as a result of the medication, and the judge ruled he should spend no further time in jail.

As the number of cases drawing on neuroscientific evidence rises steadily in Australia, and sharply in the United States, it is demanding that lawyers and judges grapple with thorny questions such as the nature of free will and moral culpability.

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"There is an increasing tendency now in the United States, and here too, to use brain-based evidence to argue that people should not be held responsible for crimes," said Dr Sascha Callaghan, a lawyer and lecturer in health law and ethics at the University of Sydney.

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In the US, lawyers for notorious Oregon serial killer Dayton Leroy Rogers, who tortured and killed eight prostitutes in the 1980s, argued this year that damage to his brain in childhood could have triggered his sadistic killing sprees.

Macquarie University's Centre for Agency, Values and Ethics (CAVE) has now joined forces with the University of Sydney to launch the Australian Neurolaw Database, a publicly available collection of Australian cases involving neuroscientific evidence, on December 8. The project was started by Macquarie University in 2011.

"Part of what we're doing is trying to work out the extent to which these powerful brain-based arguments are changing the way we think about guilt, but also changing the way we think about mental injuries and emotional injuries," said Dr Callaghan, a researcher on the project. "It breaks down the mind/body distinction."

In May, the NSW Supreme Court ordered aviation company to pay compensation to a nurse who suffered physical injuries and post-traumatic stress disorder (PTSD) after a plane crash.

Historically, PTSD has been considered a mental rather than a bodily injury and, under international law dealing with aviation injuries, compensation is not available. But the court found the PTSD was "not merely the result of an injury to her mind" – it also involved "an injury to her brain and other parts of her body".

Scientists are really sceptical about neurolaw because they say it's really pushing the science beyond what it can really tell us.

There have been predictions in some academic papers that brain research will revolutionise the legal system. But Dr Allan McCay, a senior researcher at CAVE, said, "On the ground ... it doesn't seem so revolutionary. People are looking down the track and saying, what if lie detection becomes popular or what if you can detect pain? There's a lot of peering into the future, whereas our project is a bit more like what is happening now."

In Australia, neuroscientific evidence is typically raised at the sentencing stage, when defence lawyers suggest it is a mitigating factor supporting a reduced punishment.

Questions have been raised, however, about whether visually arresting images of brain scans might encourage judges to draw conclusions that a cautious scientist would not.

"People's intuition about where justice lies gets changed by the fact that they can see these windows into people's souls," Dr Callaghan said. "Scientists are really sceptical about neurolaw because they say it's really pushing the science beyond what it can really tell us. But lawyers weave a story around it. They're trying to persuade."

There was "significant" disagreement between experts about the interpretation of brain scans but the court said they were "probably the least important basis" on which it arrived at its conclusion.

Professor Jeanette Kennett, deputy director of CAVE and head of Macquarie University's philosophy department, said research on psychopaths seemed to show "common differences in psychopathic brains and normal brains", although courts had not yet accepted this evidence.

In the future, it could be used to argue "they should be treated in some way other than punishment".

"No court is going to let you walk if you've done something really horrific, but I guess it depends what happens to you after that," Professor Kennett said.